IS SILICA A CONSTITUENT OF PLANT FOOD? 267 



No. of Ears of Corn. 



inches 24 



16 

 24 



When they were perfectly dry the stems and leaves of each 

 were separately cut up and analysed as to the percentage of 

 moisture, ash, and silica. 



The total weight of dry straw (leaves and stems) were as 

 follows : — 



Leaves. Stems. Total. 



No. 1 25.430 gms 20.130 grammes 45-55° grammes 



No. 2 25.986 „ 18.049 » 44-035 



No. 3 25.773 „ i6.59 2 » 42.365 



The average weight of one grain of wheat was found to be 

 .0447 grammes, and this had increased on an average to 43.983 

 grammes, excluding the weight of the roots and ears, which 

 would have raised this figure still further. 



The results of the analyses were as follows : — 



No. 1. No. 2. No 3. Average. 



[Moisture .. 9.49% 8.92% 11.82% 10.08% 



Leaves \ Ash . . . . 6.38% 7-53% 8.75% 7-55% 



I Silica .. .. 1.088% 1.369% 1.18% 1.212% 



No 1. No. 9. No. 3. Average. 



[Moisture .. 13.36% 10.47% I 4- I 7% 12.66% 



Stems \ Ash . . . . 7.20% 7.66% 7.27% 7-34% 



'Silica 46% -143% -7447c -449% 



Silica as it exists in sand and in rocks is virtually insoluble 

 in pure water. It may be. as some botanists suppose, that 

 plants exude from their root hairs some acid liquid which can 

 extract and dissolve silica from rocky materials in the soil, and 

 thus render it available for plant food. 



We will now contrast this low percentage of silica in the 

 leaves and stems of wheat grown in water culture solution with 

 that of some crops grown on soil : — 



Grasses. Silica. Straw. Silica. 



Meadow Hay (1st cut) 28.8% Wheat Straw 67.6% 



Sweet Grasses 36.5% Summer , 47-6% 



Sour 33-2% Bran 71-7% 



Winter Wheat (Young Winter Rye 56.3% 



Plants) 42.2% Summer , 54 T % 



Oats (Young Plants) 27.6% Barley 52.0% 



Maize (Flowering Oats 46.7% 



Plant) 18.3% 



